检索结果-南通市图书馆

A LS-SVM （Least Squares Support Vector Machines） Approach for Predicting Critical Flashover Voltage of Polluted Insulators

引用

Journal of Energy and Power Engineering 2013年第2期7卷 355-360页

作者： abdelhalim Mahdjoubi Boubakeur Zegnini Mohammed Belkheiri Studies and Development of Semiconductors and Dielectrics Materials Laboratory LeDMaScD Amar Telidji University ofLaghouat Laghouat 03000 Algeria Telecommunications Signals and Systems Laboratory LTSS Amar Telidji University of Laghouat Laghouat 03000 Algeria

LS-SVM （least squares support vector machines） are a class of kemel machines emphasizing on primal-dual aspects in a constrained optimization framework. LS-SVMs aim at extending methodologies typical of classical support vector machines for problems beyond classification and regression. This paper describes a methodology that was developed for the prediction of the critical flashover voltage of polluted insulators by using a LS-SVM. The methodology uses as input variables characteristics of the insulator such as diameter, height, creepage distance, form factor and equivalent salt deposit density. The estimation offlashover performance of polluted insulators is based on field experience and laboratory tests are invaluable as they significantly reduce the time and labour involved in insulators design and selection. The majority of the variables to be predicted are dependent upon several independent variables. The results from this work are useful to predict the contamination severity, critical flashover voltage as a function of contamination severity, arc length, and especially to predict the flashover voltage. The validity of the approach was examined by testing several insulators with different geometries. Moreover, the performance of the proposed approach with other intelligence method based on ANN （artificial neural networks） is compared. It can be concluded that the LS-SVM approach has better generalization ability that assist the measurement and monitoring of contamination severity, flashover voltage and leakage current.

关键词： LS-SVM flashover modeling polluted insulator equivalent salt deposit density.

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

State-Model Based Time-Domain Diagnosis of Internal Faults for Permanent Magnet Synchronous Machine Wind Application

引用

Journal of Energy and Power Engineering 2013年第11期7卷 2138-2143页

作者： abdelhalim Lalami Abderrazak El-Ouafi Rene Wamkeue Departement de mathdmatiques d'informatique et de gdnie University du Qudbec h Rimouski (UQAR) 300 allde des UrsulinesRimouski Qudbec G5L 3A1 Canada Departement de sciences appliquOes University du Quebec en Abitibi-TOmiscamingue (UQAT) 445 boul. de l 'UniversitORouyn-Noranda Quebec J9X 5E4 Canada

Upon occurrence of an internal fault on the PMSM （permanent magnet synchronous machine）, the topology of the stator is amended causing structural imbalances due to the change of the connection within the windings. In this work, a state model of internal faults of the PMSM is developed. This model is in the （abc） reference frame. The modeling approach is based on the assumption that each stator phase is replaced by two major and minor sub-windings. This model is used subsequently in the residual generation for diagnosis. The fault indicators are obtained by the projection in parity space and estimated using the Luenberger observer. A scenario of fault inter-turn by the short-circuit occurring between phase （a and b） is validated by simulation.

关键词： Diagnosis internal faults permanent magnet synchronous machine modeling.

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

New Analytic Solution for Ambartsumian Equation

引用

Journal of Mathematics and System Science 2018年第7期8卷 182-186页

作者： Fahad M.Alharbi abdelhalim Ebaid Department of Mathematics Faculty of ScienceUniversity of TabukP.O.Box 741Tabuk 71491Saudi Arabia

Analytical solution is obtained for Ambartsumian equation in this *** equation is of application in *** obtained solution has many advantages over the published one in the literature as shown by several comparisons.

关键词： Delay equation analytic solution

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

阿拉伯学生汉语语音习得偏误研究

阿拉伯学生汉语语音习得偏误研究

引用

作者： TASNEEM abdelhalim DAIFALLA MOHAMED（宁静）陕西师范大学

学位级别：硕士

汉语和阿语是世界上最难学的两种语言。汉语对于阿拉伯国家学生而言,有些读音是很难正确发音的、声调多变、语法也不规则、汉字则更难。因为阿拉伯国家的学生在他们的语言中没有这些难点,所以他们是第一次面对这些困难,这给他们带来不... 详细信息

汉语和阿语是世界上最难学的两种语言。汉语对于阿拉伯国家学生而言,有些读音是很难正确发音的、声调多变、语法也不规则、汉字则更难。因为阿拉伯国家的学生在他们的语言中没有这些难点,所以他们是第一次面对这些困难,这给他们带来不少的麻烦。所以为了掌握语言的基础,教师们应该从语音教学开始重视,先应该打好语音的基础,然后开始学语言的另外成分。汉语和阿语分别属于两个不同的语言系统。汉语属于藏语系,但是阿拉伯语属于闪含语系。这对阿拉伯学生来说是完全新的语言系统,学习一种新的语言系统对他们而言肯定有一些困难。语音是语言的物质外壳,是人们用他们的发音器官来发出能够表示一定的意义的声音。汉语发音不准确,导致阿拉伯国家的学生和中国人交流的时候会产生交流障碍和误解,这种交流障碍和误解长时间不解决,到之后会更加难以改变。本论文的主要研究对象是以阿拉伯语为母语并学习汉语进行对外汉语教学的学生。苏丹学生经常会犯发音错误,因为我是苏丹阿拉伯学生,也在苏丹学过汉语,所以笔者比较了解实际教学的情况是如何,本文也会结合本人的学习经验进行研究。本文也进行了阿拉伯语与汉语的语音对比研究来讨论两种语言各自的特点与它们之间的不同点。汉语语音教学工作分三大步进行,分别是声母的教学,韵母的教学和声调的教学。本文主要研究的内容是这三个步骤过程中的偏误分析、然后按照这些研究来探索这些问题的原因和怎么用最适合的方式来解决这些问题。笔者论文中会有一章是对比汉语和阿拉伯语的语音系统,以及苏丹学生学习汉语语音的偏误研究与分析。通过研究与分析,得出声母、韵母和声调教学过程中经常出现的问题。

关键词：汉语的语音阿拉伯学生声母韵母

来源：

同方学位论文库评论

在线全文

同方学位论文库

学校读者我要写书评

暂无评论

大蒜和洋葱内生真菌的分离纯化及其次生代谢产物生物活性的研究

大蒜和洋葱内生真菌的分离纯化及其次生代谢产物生物活性的研究

引用

作者： Mohamed Ahmed Faiz Ibrahim abdelhalim 兰州理工大学

学位级别：硕士

来源：

同方学位论文库评论

在线全文

同方学位论文库

学校读者我要写书评

暂无评论

Survival and outcomes for co-infection of chronic hepatitis C with and without cirrhosis and COVID-19: A multicenter retrospective study

引用

World Journal of Gastroenterology 2021年第42期27卷 7362-7375页

作者： Shimaa Afify Basem Eysa Fatma Abdel Hamid Omnia M Abo-Elazm Mohamed A Edris Rabab Maher Ahmed abdelhalim Muhammad Mostafa Abdel Ghaffar Dalia A Omran Hend Ibrahim Shousha Department of Gastroenterology National Hepatology and Tropical Medicine Research InstituteCairo 20222Egypt Department of Endemic Medicine Faculty of MedicineFayoum UniversityEl-Fayoum 13524Egypt Department of Biostatistics and Cancer Epidemiology National Cancer InstituteCairo 20222Egypt Department of Gastroenterology Students HospitalCairo UniversityGiza 12111Egypt The General Organization for Teaching Hospitals and Institutes Cairo 11562Egypt Department of Endemic Medicine Faculty of MedicineCairo UniversityCairo 11562Egypt

BACKGROUND Chronic liver disease,particularly cirrhosis,is associated with worse outcomes in patients infected with coronavirus disease 2019(COVID-19).AIM To assess outcomes of COVID-19 infection among patients with pre-existing hepatitis C with or without liver *** This multicenter,retrospective cohort study included all cases of confirmed coinfection of severe acute respiratory syndrome coronavirus 2 and chronic hepatitis C with or without liver cirrhosis who were admitted to six hospitals(Al-Sahel Hospital,Al-Matareya Hospital,Al-Ahrar Hospital,Ahmed Maher Teaching Hospital,Al-Gomhoreya Hospital,and the National Hepatology and Tropical Medicine Research Institute)affiliated with the General Organization for Teaching Hospitals and Institutes in *** were recruited from May 1,2020,to July 31,***,laboratory,imaging features,and outcomes were *** regression analysis was performed to detect factors affecting *** This retrospective cohort study included 125 patients with chronic hepatitis C and COVID-19 co-infection,of which 64(51.20%)had liver cirrhosis and 40(32.00%)***,cough,dyspnea,and fatigue were the most frequent symptoms in patients with liver ***,sore throat,fatigue,myalgia,and diarrhea were significantly more common in patients with liver cirrhosis than in noncirrhotic *** was no difference between patients with and without cirrhosis regarding *** patients(23.40%)with liver cirrhosis presented with hepatic *** with liver cirrhosis were more likely than non-cirrhotic patients to have combined ground-glass opacities and consolidations in CT chest scans:28(43.75%)vs 4(6.55%),respectively(P value<0.001).These patients also were more likely to have severe COVID-19 infection,compared to patients without liver cirrhosis:29(45.31%)vs 11(18.04%),respectively(P value<0.003).Mortality was higher in patients with liver cirrhosis,compar

关键词： COVID-19 Egypt Outcome Liver cirrhosis Chronic hepatitis C

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Minimally Invasive 360 Degrees Decompression for Ligamentous, Bony and Discogenic Lumbar Canal Stenosis

引用

Open Journal of Modern Neurosurgery 2023年第3期13卷 111-120页

作者： Ahmed Hosameldin Hussein Abdelhamid Hesham Elshetany Mostafa Abdellatif Ehab abdelhalim Department of Neurosurgery Faculty of Medicine Fayoum University Fayoum Egypt Department of Neurosurgery Faculty of Medicine Cairo University Cairo Egypt

Background: For decades, traditional open surgical techniques were used to treat lumbar disc herniation and lumbar canal stenosis (LCS). However, seeking for better outcomes for patients and avoiding extensive bony loss with its sequences had raised minimally invasive technique for treating these disorders as an alternative surgery. Methods: This is a retrospective study in which 54 patients of LCS were operated upon via unilateral minimally invasive technique to decompress the canal in a 360 degrees fashion through laminotomy, deroofing of opposite laminar side, sublaminar ligamintectomy, bilateral foraminotomies and discectomy. We used VAS scores and ODI to assess clinical outcomes with a period of one year follow-up. Results: Our results demonstrated that minimally invasive techniques for treating these disorders are effective procedures. Minimally invasive 360 degrees decompression for treating LCS had better outcomes regarding postoperative back pain, smaller incisions, less bony loss and early ambulation. Conclusion: Minimally invasive techniques for treating lumbar canal stenosis of different causes could be considered a better option instead of traditional full laminectomy with better outcomes as regards respecting the anatomical layers such as posterior spinal integrity and musculature, postoperative pain, accompanied with less blood loss, shorter hospital stays, and shorter recovery periods.

关键词： Lumbar Decompression Minimally Invasive Surgery 360 Degrees Lumbar Canal Stenosis

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Fabrication, Microstructure, Thermal and Electrical Properties of Copper Heat Sink Composites

引用

Materials Sciences and Applications 2016年第9期7卷 542-561页

作者： Walid Daoush Ahmed Swidan Gamal Abd El-Aziz Mohamed abdelhalim Department of Production Technology Faculty of Industrial Education Helwan University Cairo Egypt Present Address: Department of Chemistry Faculty of Science Al-Imam Muhammad Ibn Saud Islamic University Al Riyadh KSA Mechanical Department Ameeria Integrated Technical Cluster Cairo Egypt Mechanical Department Faculty of Industrial Education Suez University Suez Egypt

Copper as well as copper base composites reinforced with coated and uncoated 1 wt% diamond, graphite particles or short carbon fibers are prepared by powder metallurgy process. The reinforcement particles were encapsulated with silver as well as copper layer by using the electroless deposition technique to investigate the influence of the reinforcement surface coating on the microstructure, density, electrical and thermal properties of the sintered samples. The coated and the uncoated powders were cold compacted at 600 MPa, and then sintered at 1173 K (900°C) for 2 h under hydrogen atmosphere. The phase composition, morphology and microstructure of the prepared powders as well as the copper base sintered composites were investigated using X-ray diffraction analysis (XRD) and Scanning Electron Microscope (SEM) equipped with an Energy Dispersive Spectrometer (EDS) respectively. The density of the sintered composites was measured by Archimedes method. The copper base consolidated composites had a density up to 96% and the reinforcement coated particles were distributed uniformly within the copper matrix better than the uncoated one. The electrical resistivity at room temperature and the heat transfer conduction of the produced samples were measured in a temperature range between 323 K (50°C) and 393 K (120°C). The results observed that the sintered materials prepared from the coated powder have lower electrical resistivity than the sintered materials prepared from the mixed powders. On the other hand the thermal conductivity values were calculated using the heat transfer conduction values by means of the Fourier formula. The results observed that the thermal conductivity of copper is (391 W/m·K), 1 wt% diamond/Cu is (408 W/m·K), 1 wt% graphite coated silver/Cu is (393 W/m·K), 1 wt% Cu coated short carbon fiber/Cu is (393 W/m·K), graphite/Cu is (383 W/m·K) and short carbon fiber/Cu is (382 W/m·K). The obtained compos

关键词： Heat Sink Powder Metallurgy Matrix Composites Electrical Resistivity Thermal Conductivity Natural Forced Convection

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

埃及股票市场资产定价模型比较研究

埃及股票市场资产定价模型比较研究

引用

作者： Mahmoud Abdelrahman Mohamed abdelhalim Elshazly 西南财经大学

学位级别：硕士

探究一种行之有效的资产定价模式,不仅能为广大投资者构筑更好地投资策略,同时还能对市场监管者的决策提供支持。因此,为了更加深入的对埃及股票市场中资产定价模型的差异性进行研究,进而识别埃及股票市场股票收益的决定因子。本文检验... 详细信息

探究一种行之有效的资产定价模式,不仅能为广大投资者构筑更好地投资策略,同时还能对市场监管者的决策提供支持。因此,为了更加深入的对埃及股票市场中资产定价模型的差异性进行研究,进而识别埃及股票市场股票收益的决定因子。本文检验了相关的因子模型是否能捕捉到埃及股票市场的收益变化,并研究了这几种模型在埃及证券交易所的定价效率,比较这几种模型的表现,以此内容为相关学术研究和从业者提供一定的参考建议。在当今历史背景下,疫情对于EGX带来了不可预期的熊市,埃及股票市场处于现在的时代背景下,其市场地位是不容忽视的。同时,EGX是中东地区最早成立的交易所之一。如果从埃及政府实施私有化计划开始计算,埃及交易所自重组以来不超过30年,股票市场的许多基础设施相较纽交所来说还不太健全。然而,目前绝大多数因子模型的构建及检验,主要集中与美国股市这一成熟市场的研究,针对埃及交易所的分析显得寥寥无几。因此,本文对于埃及证券交易所的研究也具有一定的现实意义。本研究的目的是检验Fama-French三因子模型、Carhart四因子模型和Fama-French五因子模型能否解释埃及股票市场的股票收益,文中选取了来自 Thomson Reuters DataStream,Egypt for Information Dissemination(EGID)的数据集,该数据集代表2012年至2022年6月埃及证券交易所的每周股票交易价格,并利用文献研究法、实证研究法和理论分析法得出结论。(1)文献研究法。结合研究问题,研究与整理了这个领域的相关内容和研究成果,发现并总结出现有研究的不足之处,从而确定了本文下一步的主要研究方向与研究内容。(2)实证分析法。测试Fama-French三因子模型,Carhart四因子模型,Fama-French五因子模型,如何测量模型变量、投资组合构建和GRS测试,A|ai|,A|ai|/A|ri|,A(∝i2)/A(μi2)。(3)理论分析法。相关学者关于因子模型开展了较为丰富的理论模型和实证研究,通过对相关文献的梳理和归纳,使得本文的论题具有扎实的理论基础。因此,对埃及股票市场资产定价模型在该领域发展有了比较透彻的理解。在综上所述的研究方法下,获得了以下几条结论:(1)通过检验Fama-French三因子模型、Carhart四因子模型和Fama-French五因子模型等经验资产定价模型后,发现Fama-French五因子模型可以有效捕捉埃及股票市场平均股票收益的变化是与β因子、规模因子、价值因子、动量因子、投资因子、盈利因子有关。(2)埃及的股票市场存在规模因子、价值因子、动量因子、投资因子和盈利因子的模式。(3)本文将Fama-French五因子模型与Fama-French三因子模型进行比较,综合辨识文中所示因子与这些因子在回归模型中的系数及其显著特征,最终得出在五因子模型中,规模因子跟账面市值比具备该模型最主要的解释力特征。投资风格因子CMA受市值规模大小跟账面市值比高低干扰较多,将投资风格变量细分,验证其在在市场规模干扰下,对超额收益率的显著性影响,发现此时CMA因子显著情况明显增加,最终判断投资风格也是超额收益率显著的影响因子,同时也说明了五因子模型比三因子模型解释力更强,埃及股票市场在Fama-French五因子模型中更适用。

关键词：资产定价 Fama-French五因子模型埃及股票市场

来源：

同方学位论文库评论

在线全文

同方学位论文库

学校读者我要写书评

暂无评论

Results of the Sauvé-Kapandji Procedure for Posttraumatic Disorders of the Distal Radioulnar Joint in Young Patients

引用

Open Journal of Orthopedics 2015年第3期5卷 35-40页

作者： Hatim Abid Mohammed Shimi abdelhalim El Ibrahimi Abdelmajid El Mrini Department of Osteoarticular Surgery B4 HASSAN II Teaching Hospital Fes Morocco

The authors report their experience with the Sauvé-Kapandji procedure for the management of posttraumatic disorders of the distal radioulnar joint in 9 younger and active patients. The mean age of our series was 37 years. We operated patients for whom pain in the distal radioulnar joint was more relieved by usual analgesic medical treatment, and those with a limitation of wrist movements. Until the latest follow-up, patients have benefited from antero-posterior and profile radiographs of the wrist. Functional assessment was based on the Modified Mayo Wrist Score whose average value was around 77 points. Postoperatively all patients experienced relief of pain. Rotation of the forearm increased to near normal values. On a professional level, eight of nine employed patients had returned to work. There were no major complications.

关键词： Posttraumatic Disorders Distal Radioulnar Joint Sauvé-Kapandji Procedure

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：